Wire bonding has been used in integrated circuit packaging since the inception of IC technology. Wire bonding techniques and wire bonding machines have been refined to the point where wire bonds are relatively inexpensive and are highly reliable. However, wire bonds are rapidly being replaced by more advanced packaging approaches, partly because wire bonds require greater pitch than is available in many state of the art packages.
Among the advanced IC packaging approaches is silicon on silicon technology. Use of silicon interconnection substrates is becoming attractive for high density packages wherein high pin count IC chips are flip chip bonded to a silicon intermediate interconnect substrate, and the silicon intermediate interconnect substrate is in turn ball bonded or flip-chip bonded to a printed wiring board. In many cases these packages use recessed chip arrangements to reduce the package profile.
In these advanced packaging approaches, interconnection pitches can be very small. The earlier technology of wire bonding has been left behind since the high density of I/O's in current IC chips presents a challenge to the capacity of wire bond techniques. However, largely due to the high I/O density of state of the art IC chips, packaging yield using advanced packaging techniques may suffer, and the complexity of the packaging process is increased. As a result the overall cost per bond may be relatively high. The low cost and high reliability of wire bonds makes them attractive if ways can be found to adapt wire bonding to packaging high density I/O chips.